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I was talking to a gentleman that is building a retire home 33 miles out of Key West. I am located in Toronto Canada and he was telling me that the temperature in Key West area never goes above 90 F. He is thinking that he should need the same size of A/C equipment in Key West as in Toronto. I told him that it was hard to believe and he should a heat gain done. He then mentioned that the reason he dropped by was that he has a quote from a local contractor to supply 10 tons of cooling. He thinks the contractor is off his rocker. I asked about a heat gain, and he said the contractor gave him drawings but no calcs. The home is new construction with R19 walls and r40 ceiling, 3200 square ft 2 storey with shaded glass. Ocean in back yard and across the street thus a constant breeze his wife mentioned. They also stated that they ddnt want A?C but were told that local code requires AC in a new home. I told him I would ask a few questions on this site. Any ideas on 10 tons being too much? Thanks Jim

Sounds high to me since the house appears to be well built. Probably someone who sizes by the sq ft! Tell him to demand an accurate load calc. We build them that well, without an excess of windows, we'd probably put about 4 tons in that size house. But of course, I'm not doing anybody any good by guessing

Not only that, Key West often has LOWS in the mid 80's at night. 'though temp's the least of your worries there -- humidity's the primary concern. That's one area where a separate dehumidifier makes great sense, especially some of the whole-house ones.

Get It Right THE FIRST (& Only) Time

Originally posted by jchaters building a retire home 33 miles out of Key West.

The home is new construction with R19 walls and r40 ceiling, 3200 square ft 2 storey with shaded glass. Ocean in back yard and across the street thus a constant breeze his wife mentioned. Thanks Jim

Jim,

NO WAY is 10 tons necessary with that GOOD insulation
And significant amount (~ 650 Square Feet total)
of windows with S.H.G.C. < 0.5.
Also, spray foam insulation in the attic and
very light color metal roof would be great for
"in the middle of the ocean."

I do not believe R-40 Ceiling insulation addressing an overall, value engineered design. 5" of spray foam at
~R-19 with inherently reduced infiltration seems to be more appropriate for this house and Location.

I am sure TPA-FL knows as do other FL professionals that A/C addresses building envelope characteristics, not just Manual J sizing, selection and installation. For example, Whole-house dehumidifier is a great recommendation.

A 10-Ton system WILL CREATE Mold problems like
one would only wish on the devil.

Originally posted by jchaters I was talking to a gentleman that is building a retire home 33 miles out of Key West. I am located in Toronto Canada and he was telling me that the temperature in Key West area never goes above 90 F. He is thinking that he should need the same size of A/C equipment in Key West as in Toronto. I told him that it was hard to believe and he should a heat gain done. He then mentioned that the reason he dropped by was that he has a quote from a local contractor to supply 10 tons of cooling. He thinks the contractor is off his rocker. I asked about a heat gain, and he said the contractor gave him drawings but no calcs. The home is new construction with R19 walls and r40 ceiling, 3200 square ft 2 storey with shaded glass. Ocean in back yard and across the street thus a constant breeze his wife mentioned. They also stated that they ddnt want A?C but were told that local code requires AC in a new home. I told him I would ask a few questions on this site. Any ideas on 10 tons being too much? Thanks Jim

Key West will not get much hotter than low 90s. I am a Canadian on an island quite a bit south of Key West and I design around 91F.

It will be a lot more humid than Toronto. As well, the sun plays a different role in Key West than in Toronto.

The insulation levels sure sound like a Canadian Architect drew up the plans. The climatic effects here, especially concerning humidity and vapour barriers are all opposite to they way it works in Canada.

It is only a matter of time before Key West is struck by a hurricane so your friend should heed the story of the three little pigs. Anyone living in the hurricane belt should build out of concrete. A hurricane is more than just strong winds, it involves flooding and a concrete building stands up to water a lot better than wood and sheet rock.

Framed construction allows the possibility of walls becoming air ducts for humid outdoor air which will get filtered by the R19 - this can lead to condensation problems and mold. Framed walls also make good ant farms.

If he insists on framing the walls go with the icynene (sp?) sprayed in foam insulation.

10 tons sounds very high unless there is some sort of solarium with walls of all glass. If that is the case on a cloudy day, there will be minimal heat in through this glass and nothing to trigger the thermostat to make the AC run. The AC will be off for extended periods of time yet the humidity will be there. When the AC does not run it will not remove humidity. Compound this with the fact that this could be a vacation home, with unoccupied periods and I would install a dehumidifier system as well.

Just some comments from a Canadian NW of Toronto who has been in the islands for close to seven years now.

The way we build has a greater impact on our comfort, energy consumption and IAQ than any HVAC system we install.

Dan brought up a good point about sea coast. The salt air will eat up condensing units as quick as road salt eats up cars in NW Ontario.

Trane and American Standard units have all aluminum spine fin coils that stand up well to salt corrosion.

Last point, concerning roofing.When I build I will have a concrete roof deck with trusses over top basically for looks and to create some storage space. We were hit by a Cat 5 storm here and the roof covering that stood up the best was standing seam.

Your friend knows what he wants, but 3200 sq feet is a lot of space for a retirement home, sounds like ample spare bedrooms for the kids/grand children to visit. Could build something smaller and a lot more sturdier for the same money.

The way we build has a greater impact on our comfort, energy consumption and IAQ than any HVAC system we install.

ok.....Let Him Build The Castle...and under cool it....Or Over Cool it... I have seen A Lot Of POS There....Carnack Is wright....Let Him Design It.....Then Find a good Contractor To Put It in......Import One from South Florida....In The Keys, They Only Give Out So Many New Construction Permits a Year.....Most Of The shops there, Don't Make New Construction A Top, In There Business......mostly Change outs....Seen Some Pretty Sad work In The Lower keys......Key West Contractors Just as High As Hawaii......Lot More Money Than KY.

Refrigeration...Finding the Wright Wrench to pound in the correct..Screw